Thin polished plates such as silicon wafers and the like are a very important part of modern technology. A wafer, for instance, may refer to a thin slice of semiconductor material used in the fabrication of integrated circuits and other devices. Wafers are subject to defect inspections, and scanning electron microscope (SEM) inspection is considered one of the most sensitive forms of defect inspection for wafers.
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a target (e.g., a wafer) by scanning it with a focused beam of electrons. The electrons interact with atoms in the target, producing various signals that contain information about the surface topography and composition of the target. It is noted that the throughput of a SEM may be increased by increasing the number of focused beams of electrons (providing a SEM known as a multi-beam SEM). It is also noted, however, that currently available multi-beam SEMs do not support multi-beam dark field imaging.